Once you come to a stop and the arrow is displayed you have to press ok to start it off. The first thing you have to do us reverse straight back until it beeps. Then stop. Then turn the wheel until it beeps. Hold and move back until it beeps again, and stop. Then move the wheel as shown again until beep. Hold and move back until beep.
It is very accurate but I agree a real faff. At the end of the day, I believe that if you can't park it yourself, don't drive it. I tried it out once to see what it was all about. Not used it again.